Bicycle riding is an efficient mode of transportation that provides exercise as well as enjoyment. Because they are human-powered, this activity requires no fossil fuels (an increasingly important consideration). First developed long ago, bikes can be found throughout the world. Some individuals have even pedaled them across continents.
The frame of a bicycle supports two wheels situated along the frame's centerline, with the front wheel serving as the steerable wheel used to control the vehicle's direction and the rear wheel serving as the drive wheel receiving power input from the rider. A typical bicycle frame has a top tube, a seat tube, a down tube, a head tube, two seat stays, two chain stays, and a bottom bracket shell. (Some bikes intended for women have a top tube that attaches lower down on the seat tube compared to a man's bike.) The steerable front wheel is secured to front forks installed in the head tube, and the fixed rear wheel is situated between the seat stays and chain stays. The seat—sometimes called a saddle—is located above the top tube and is normally attached to the frame via a seat post arrangement.
Young children usually begin their riding adventures aboard tricycles which, due to the three wheel design, have greater stability than bicycles. (A vehicle having three wheels in simultaneous contact with the ground reflects the stability of a tripod.) When their sense of balance has sufficiently developed, many kids move up to the two-wheeled vehicle variety.
A child's trike has a steerable wheel in front and two fixed wheels in the back. The front wheel is connected to a handlebar which enables the user to turn the wheel and change the vehicle's direction of travel. Pedals attached to the front wheel provide the means by which the operator contributes propulsive effort.
The frame of a child's tricycle is a rather simple affair, providing places of attachment for a seat as well as the two rear wheels. A front fork holds the front wheel.
There are so-called “adult tricycles”, the frames of which resemble in many respects a bigger form of the children's version. Like a child's trike, these vehicles have one steerable wheel in front and two at the rear in a fixed position. The front wheel is secured to the frame at a front fork. Again, a handlebar provides a user with the ability to turn the front fork and thereby control the front wheel. The rear wheels are attached to the frame at portions of the frame which branch out from the frame's centerline.
Turning an adult tricycle is similar to controlling a bicycle. The user rotates the handlebar such that the handlebar rotates about a pivot point.
The primary difference between the adult tricycle and the one meant for a child is that in the adult version the pedals are affixed to crank arms secured at a low point on the trike's frame with a ball bearing setup known as a bottom bracket, similar to the arrangement on a bicycle. A sprocket attached to the crank arms then exerts force on a drive chain which runs to another sprocket on a transverse axle connecting the two rear wheels. Downward pressure on the pedals moves the crank arms and pulls on the chain, resulting in forward motion. Another difference between a child's tricycle and the one used by grownups is that adult tricycles often utilize hand brakes.
Usually a cargo basket is situated between the rear wheels of an adult tricycle to facilitate the transportation of groceries or whatnot.
Adult tricycles are “upright” designs, where the rider sits astride the seat and stands on the pedals. That is, the crank arms are placed for the most part in a space below the seat. This is the arrangement used on most bicycles, like city bikes, road bikes, and mountain bikes. (The standard upright bicycle frame is sometimes referred to as the “diamond frame” in reference to its shape.)
These adult tricycles are popular and serve many functions. For example, they are used by those who have motor-balance issues which prevent the individual from riding a bicycle. A number of these riders could very well be elderly persons who still want to enjoy cycling yet don't feel comfortable doing so on a two-wheeled vehicle. The adult tricycle provides them with a viable alternative.
There are also younger riders who, for one reason or another, find adult tricycles useful. Some of these individuals have a physical limitation which prevents them from operating a bicycle. For them the adult tricycle's stable platform is the only option for cycling.
But in fact other applications for these vehicles abound. They have been used by food vendors and delivery persons alike. The stability three wheels offers not only simplifies hauling a load but also remains steady after the rider dismounts, thus eliminating the need for a kickstand. Adult tricycles are also employed in warehouses, at assembly plants, and on factory floors. In this capacity they provide a non-polluting form of transportation for efficiently moving about people and supplies. The vehicles furthermore tender a secondary benefit to the workers operating them by the possibility of improved physical fitness.
Even someone able to safely ride a bicycle might prefer an adult tricycle in certain situations. Case in point could be a watersports enthusiast transporting a bulky/unwieldy object (e.g., a stand-up paddleboard or a sea kayak) to the shore. A trailer holding the transport item and towed by an adult tricycle would likely be a less problematic experience than towing the same trailer with a two-wheel bike.
[NOTE: A three-wheel vehicle will have greater potential braking authority than a bicycle simply because, by virtue of an additional wheel, it has more ground contact and can thereby exert more stopping friction. This provides a performance gain when transporting heavier items or descending steep inclines.]
Though they are extremely useful, adult tricycles are not without disadvantages. First and foremost among these disadvantages is that a three-wheeled vehicle with one wheel in front and two at the rear can lose platform stability when cornering if it is moving too fast. Centrifugal force acting upon the user's body tends to pull the rear wheel on the inside of the turn off the ground. If this happens and the user fails to regain control, the tricycle will tip over.
(This is the reason the All Terrain Vehicle—or ATV—industry no longer manufactures a three-wheeled version of these machines. Those vehicles were accident-prone and caused many injuries. The four-wheeled “quad” set-up, with two wheels in front, is now standard.)
The prior art offers some recumbent trike designs, intended for adults, which place two wheels in front with a single drive wheel in back. (Recumbent tricycles and bicycles place the rider in a reclining position such that, when pedaling, the rider's legs are essentially horizontal to the ground because the pedals are more or less level with the seat.) These arrangements appeal to some users, but not everyone is comfortable riding them. There are individuals who find getting in and out of a recumbent trike physically difficult because the seat sits so low to the ground. Also, there's a safety issue in that motor vehicle drivers might be less likely to spot a recumbent trike rider than they would the rider of an upright tricycle or bicycle. Recumbent vehicles (there are recumbent bicycles as well as tricycles) could be concealed by things like parked cars, whereas the upright tricycle or bicycle presents a taller profile. Many riders also go with the upright cycle variety purely as a matter of personal preference. (Upright cycles are easier to pedal uphill because the rider can use their body weight to apply force to the pedals.) A final feature of incumbent trikes which diminishes their usage is that the space between the two front wheels—which would otherwise be the ideal location for a cargo basket—is occupied by the crank arm/pedals assembly used to propel the vehicle. Once the rider's legs are added, there's simply no room for anything else in the area. This aspect of recumbent tricycle limits their utility. For these reasons the upright adult tricycle design suits many users better. Recumbent cycles are not for everybody.
However, there's still another major disadvantage of the conventional adult tricycle: its bulk. Adult tricycles take up far more space than a bicycle. This can be a problem for someone who desires to cycle to work, for example, but who also must use public transportation for part of the commute. Bicycles can easily be taken aboard a subway train or stowed on a city bus bike rack, but this is not the case with an adult tricycle. (And try to imagine taking an adult tricycle onto a subway escalator or into a busy elevator car.)
Therefore, a pedal-propelled three-wheel upright, one person vehicle design placing two wheels in front and a single fixed wheel at the rear would have value. The dual front wheel arrangement would improve upon the adult tricycle's tendency to tip when executing a turn, hence contributing to enhanced vehicle stability. The upright arrangement would appeal to users who favor this arrangement over recumbent vehicles. And if the two front wheels were both steerable, this would result in improved steering control over the prior art adult tricycle because two wheels provide more traction than a single wheel (especially when cycling on loose ground, such as trail biking). In addition, if a steering mechanism could be devised that not only enabled the rider to control the vehicle but also permitted the two front wheels to be decoupled so as to move independently when the vehicle is not in use, the frame could be made foldable. The preferred embodiments address these needs by providing an innovative alternative to the traditional adult tricycle, resulting in a versatile cycling apparatus that opens up more transportation and recreation possibilities.